Electric to hydraulic brakes

[dogsbreath]

I was reading in another forum where a member had modified an ABS pump to drive his hydraulic trailer brakes. I have seen ABS modules but none with a pump connected. What vehicles utilise this system and how might it be modified to suit the trailer brakes.?

[Godzilla]

Maybe a link to the thread where you saw this mod may assist us in understanding exactly how you want this to work.

Sounds like its taking the ABS signal from the car and running it to a separate ABS unit on the trailer to replicate its function.

Post a link to clarify things.

[dogsbreath]

We are looking at a electric over Hydraulic brake control for a boat trailer.
Not wanting to convert axles to standard electric brakes as a lot of money has already been spent on stainless and galvanised running gear + standard electric gear would not handle salt contamination very well.

In the linked thread the comment below is made which took our attention and got us thinking.

"Eric Experience. replied:
Collyn
Not the answer you are looking for, but I overcame the same problem by using the brake control as a current proportional to braking effort to drive a modified abs pump, the pump was running in a stalled mode but the current is low, so is not enough to burn out the armature. Eric. "



There are devices on the market like the "Dexter" unit.


The Dexter unit is priced at about $1250 which isn't an issue, other than trying to stop it from being ripped off in the carpark.
However there is some concern that some of these units require their own specific controllers and won't work with standard tekonsha type controllers. We have also heard some negative feedback by owner/operators on similar other branded units to the Dexter.

Regards Craig

[Godzilla]

Ok now im starting to understand how and what you are trying to achive.

The ABS system units have a pump and built in valve for each wheel it controls. IE; a large block with 4 valve units (one for each wheel) and a pump built into it.
Pretty much most of the systems ive seen are like this, they are all in one unit.

Each brake line that the ABS controls, that is that each wheel that has a pulse sensor (a sensor at each wheel that collects pulses that reads what speed the wheels turning at), has a matching Valve inside the ABS unit for that wheel, a controller processes the sensors data, starts the pump and sends valve commands to the ABS unit.

These valves have 3 positions.
In position 1 the valve is wide open and pressure from your master cylinder (brake pedal) passes straight through. Its running with no ABS input just like a non ABS car until the controller senses a wheel traveling slower than the others under braking.
In position 2 the valve closes and blocks the line, stopping any pressure from the master cylinder (brake pedal) getting higher or lower. It therefor holds the pressure in the system at the time it closed.
In position 3 the valve opens and releases all pressure, regardless of how hard you push on the brake pedal.

The pump is used as a way to get the pressure back up when the valve opens to release pressure, when needed. The pressure removed (release the brake) needs to be replaced (apply the brake). In ABS mode, the system is running the valves in postion 2 and 3. Brake (lock), unlock. Its pulsing between the 2 positions.

Yep could be done, but what you need is a controller to replicate the wheel sensors and therefore the control of the unit some how by controlling the time that the 2 valve postions (2+3) are working for.

You need to understand trailer controllers which i dont.

What you need is a controller that can start the pump and therefor increase the brake pressure remotely (say taken your brake light switch) and control the valve position to close the valve and open it to release it (position 2 and 3) in a pulsing type of method. The amount of time the valve does not open to release the pressure is the amount of pressure your applying to the brakes. The longer you open the valve the less braking you are applying.

I hope this helps you understand it a little.

[dogsbreath]

The prodigy brake controller is a proportional controller which measures Decceleration and applies an appropriate amount of power to the electric brake solenoids. I do not know wether this is via a voltage/current control or a pulse width control system. The impression I had from this was that the output of the controller could directly feed to the pump which would then apply varying amounts of pressure to the calipers.




I am thinking along the lines of using a reservoir to supply the pump with fluid. The output direct to your calipers along with a bypass and suitably selected orifice to return fluid back to the reservoir to prevent dead heading and stalling of the pump. A series resistor may also be selected to match output of the controller to the pump. A breakaway battery system could also be added to power pump in a breakaway circumstance.
I have not seen ABS units like shown in the above link where the pump is quite obvious.